According to the Gentoo Sparc manual, you can use ext4 for your root partition, http://www.gentoo.org/doc/en/handbook/handbook-sparc.xml?part=1&chap=4 However, while I didn't have problems booting 3.8.8 onto a ext3 disk, that disk was too small and I moved everything over to a ext4 formatted new drive. Unfortunately, all seems to go well and the bootconsole even says it mounts root as ext4, then devtmpfs, but then all messages stop, and I can't access the machine from ssh as before. In other words, its a bit hard to see what's wrong. Now, I know I can net boot and check the log files, or it might be possible to set up a serial console, but, being a bit lazy, I just wanted to ask:

Is it possible to put root on ext4 for sparc running silo? Has anyone tried it?

I've done it on a U10, so yes. The U10 might be a bit of a special case though.
It has the worst IDE chipset in the world and it has to be booted from that, unless you netboot.
I have /boot on an IDE drive and everything else on a 160G PCI SATA card, so root was ext4.
Boot is still ext2._________________Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.